1. Field of the Invention
The present invention relates to an information recording and reproducing apparatus and more particularly to an information recording and reproducing apparatus in which a card carriage is guided by a pair of guide rails to reciprocate through a predetermined stroke.
2. Description of the Related Art
In an information recording and reproducing system using an optical memory card as an information storage medium, the optical memory card is moved linearly forward and rearward relative to an optical recording and reproducing head and the optical head scans a data track on the optical memory card to write and read information into and out of the optical memory card.
In such conventional system, a drive means such as a linear motor moves a card carriage in rectangular form through a predetermined stroke at a high speed so that the optical memory card carriage is guided by parallel main and auxiliary guide rails having circular cross sections. Conventionally, the main and auxiliary rails extend in a travel direction of the optical memory card, and bearings of the card carriage having bearing bores of the round cylindrical form engage the two guide rails. Since it is difficult to obtain an accurate parallelism of the two guide rails, it is difficult to smoothly move the card carriage. In order to overcome this drawback, a technique has been developed by which the card carriage engages the main guide rail by means of a main plain bearing having a bore with the edge surface in close contact with the cylindrical surface of the main guide rail and by which the card carriage engages the auxiliary guide rail by means of an auxiliary plain bearing having a U-shaped groove, so that the bottom surface of the groove is in sliding contact with the auxiliary guide rail.
The prior art information recording and reproducing system has the following drawback. While the main plain bearing is sufficiently durable for longtime service since the main plain bearing has a round cylindrical bore the overall edge surface of which is in sliding contact with the main guide rail, the auxiliary plain bearing is in line contact with a certain portion of the auxiliary guide rail. Therefore, wearing due to this line contact tends to occur during use of the apparatus and the auxiliary plain bearing has poor durability. The wearing makes it difficult to maintain the level of the upper surface of the card carriage at an initial level, so that a predetermined distance for recording and reproducing data between the optical recording and reproducing head and the optical memory card cannot be accurately maintained. Since the card carriage experiences oscillation due to the wearing at a certain position in the bearing surface of the auxiliary plain bearing, the card carriage does not stably reciprocate. This adversely affects recording and reproduction of the information on and from the optical memory card.
In addition, the card carriage is usually mounted within an apparatus case. The front portion of the apparatus case has a front panel mounted thereon and having a card receiving slot.
Recently, there has been a tendency to reduce the thickness of the apparatus case tends. This entails the drawback that a reduced distance between a mounting surface to which the apparatus is mounted and the card receiving slot may result in contact a of hand or fingers of an operator holding the optical memory card with the mounting surface. Therefore, it is difficult to insert the optical memory card into the card receiving slot.